Easy semver for github-flow

SEMVER

# semver: increment MAJOR version when you make incompatible API changes
# magic number 4b825dc642cb6eb9a060e54bf8d69288fbee4904 is git commit hash of null (before init commit)
MAJOR_VERSION=0
MAJOR_LAST_COMMIT_HASH="4b825dc642cb6eb9a060e54bf8d69288fbee4904"

# semver: increment MINOR version when you add functionality in a backwards-compatible manner
MINOR_LAST_COMMIT_HASH=$(git rev-list --invert-grep -i --grep='fix' ${MAJOR_LAST_COMMIT_HASH}..HEAD --no-merges -n 1)
MINOR_VERSION=$(git rev-list --invert-grep -i --grep='fix' ${MAJOR_LAST_COMMIT_HASH}..HEAD --no-merges --count)

[ "${MINOR_LAST_COMMIT_HASH}" = "" ] && MINOR_LAST_COMMIT_HASH=${MAJOR_LAST_COMMIT_HASH}
[ "${MINOR_LAST_COMMIT_HASH}" = "" ] && MINOR_VERSION="0"

# semver: increment PATCH version when you make backwards-compatible bug fixes
PATCH_VERSION=$(git rev-list ${MINOR_LAST_COMMIT_HASH}..HEAD --no-merges --count)
echo ${MAJOR_VERSION}.${MINOR_VERSION}.${PATCH_VERSION}